CA2058815A1 - Method of improving the rated load heat rate of steam turbines - Google Patents
Method of improving the rated load heat rate of steam turbinesInfo
- Publication number
- CA2058815A1 CA2058815A1 CA 2058815 CA2058815A CA2058815A1 CA 2058815 A1 CA2058815 A1 CA 2058815A1 CA 2058815 CA2058815 CA 2058815 CA 2058815 A CA2058815 A CA 2058815A CA 2058815 A1 CA2058815 A1 CA 2058815A1
- Authority
- CA
- Canada
- Prior art keywords
- steam
- flow
- turbine
- steam flow
- nozzle ring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 11
- 230000000903 blocking effect Effects 0.000 claims abstract description 7
- 230000006735 deficit Effects 0.000 claims abstract 3
- 239000012530 fluid Substances 0.000 claims description 5
- 238000012544 monitoring process Methods 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 239000002803 fossil fuel Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
Landscapes
- Control Of Turbines (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
Abstract
56,267 ABSTRACT OF THE DISCLOSURE
A method and apparatus for minimizing heat rate impairment from excess flow margin in a nuclear powered utility steam turbine generating system incorporates a plurality of selectively positionable plug members for blocking steam flow passages through a first stage nozzle ring of the steam turbine.
Monitoring apparatus determines when the steam flow through a control valve feeding steam into the steam turbine exceeds a desired flow rate value for the power system and thereafter selectively inserts plug members into position in front of flow passages between adjacent nozzle blades in the first stage nozzle ring. The plug members effectively reduce this flow rate through the nozzle ring without requiring throttling of steam by the control valve. Utilizing the plug members to block steam flow through selected passages in the first stage nozzle ring allows control of the volume of steam flow through the ring without the inefficiencies attained when throttling the control valve is used to control steam flow.
A method and apparatus for minimizing heat rate impairment from excess flow margin in a nuclear powered utility steam turbine generating system incorporates a plurality of selectively positionable plug members for blocking steam flow passages through a first stage nozzle ring of the steam turbine.
Monitoring apparatus determines when the steam flow through a control valve feeding steam into the steam turbine exceeds a desired flow rate value for the power system and thereafter selectively inserts plug members into position in front of flow passages between adjacent nozzle blades in the first stage nozzle ring. The plug members effectively reduce this flow rate through the nozzle ring without requiring throttling of steam by the control valve. Utilizing the plug members to block steam flow through selected passages in the first stage nozzle ring allows control of the volume of steam flow through the ring without the inefficiencies attained when throttling the control valve is used to control steam flow.
Description
\\
- l - 56,267 NETHOD OF IMPROVING THE RATED LO~D H~A~ R~TE
OF ST~AM ~URBINES
BACXGROUND OF THE INVENTION
Steam turbines are delivered with warranties of stated power. For fossil fuel systems, stated power is related to power output of the turbine. However, in nuclear powered systems, the NRC licenses the power generating system in terms of the heat energy input to the turbine. It has been the practice in eit~er type of system to assure that the warranted power is available by oversizing the turbine, i.e., by providing more flow capacity than has been calculated as necessary to produce the warranted power. This added flow capacity is generally referred to as flow margin and is often selected to be about five percent.
In fossil fuel systems, the flow margin operates to the benefit of the user and merely provides more power output capability. However, in nuclear field systems, the flow margin may re~uire valve throttling at full ; operating power to limit the input power to the licensed NRC speclfications for that system.
Unfortunately, throttling reduces efficiency of the turbine system.
, ~5~
- l - 56,267 NETHOD OF IMPROVING THE RATED LO~D H~A~ R~TE
OF ST~AM ~URBINES
BACXGROUND OF THE INVENTION
Steam turbines are delivered with warranties of stated power. For fossil fuel systems, stated power is related to power output of the turbine. However, in nuclear powered systems, the NRC licenses the power generating system in terms of the heat energy input to the turbine. It has been the practice in eit~er type of system to assure that the warranted power is available by oversizing the turbine, i.e., by providing more flow capacity than has been calculated as necessary to produce the warranted power. This added flow capacity is generally referred to as flow margin and is often selected to be about five percent.
In fossil fuel systems, the flow margin operates to the benefit of the user and merely provides more power output capability. However, in nuclear field systems, the flow margin may re~uire valve throttling at full ; operating power to limit the input power to the licensed NRC speclfications for that system.
Unfortunately, throttling reduces efficiency of the turbine system.
, ~5~
- 2 - 56,267 One method of overcoming the loss of efficiency resulting from throttling is to provide for partial arc control of the steam turbine. Partial arc admission is achieved by dividing steam which enters the turbine inlet into isolated and individually controllable arc~ of admission. In this method, the number of active first stage nozzles is varied in response to load changes. Partial arc admission turbines attain a relatively high ideal efficiency by sequentially admitting steam through individual nozzle chambers with a minimum of throttling, rather than by throttling the entire arc of admission.
In nuclear powered steam turbines where maximum allowable steam flow is limited by the licensed reactor power, excessive flow margin results in efficiency losses. In addition, two-phase flow effects were often inadequately predicted in many nuclear turbine designs and have contributed to reduced first stage exit pressure, increased flow capacity, and a resultant off-design performance of the first turbine stage. These effects require excess throttling of the control valves to maintain licensed reactor power. These same two-phase effects also reduce extraction pressures of the turbine feedwater heaters resulting in reduced final feedwater temperature and enthalpy. These latter effects culminate in a red~ction in steam generator flow in order to maintain warranted power at the licensed level producing further throttling of the control valves. If the flow margin is reduced, the risk of inadequate power is increased.
Increasing the number of valve points would allow reduction of the amount of flow that might be throttled at rated power. Referring to FIG. l, an - 3 - 56,267 examination of the valve loops lO and 12 in comparison with the valve loops 14, 16, and 18 will readily demonstrate the heat rate improvemsnt in adding a valve point at 87.5 percent ~low and at 62.5 percent flow. However, each valve point requires addition of a control valve and its attendant steam piping with a significant increase in capital cost.
In general, partial arc admission provides a limited range of control and is combined with some degree of throttling of input steam. For example, the first stage flow area of a turbine may be divided into four, six, or eight partial arcs o~ admission with the smallest arc representing 12% of the first stage nozzle area. Clearly, if the flow margin is set at a maximum of 5%, some degree of throttling is requiredt with an attendant loss of efficiency, if steam flow is to be varied by an increment less than 12%. In partial arc turbines, each arc of admission, whether it be 25% or 12.5%, is associated with a separately controllable steam control valve so that steam flow to each arc can be controlled. Each control valve is relatively large and coupled to steam pipes of several inches in diameter in order to accommodate the large flow rates in power utility turbines. Most turbines of the partial arc type are so crowded by control valves and piping that additional val~es and their associated steam piping are not practical thus prohibiting use of valves capable of control partial arc segments to less than 5%. It is desirable, therefore, to provide a method and apparatus for regulating steam flow in increments less than 5%
without the steam throttling and without adding additional control valves and piping.
~8~
In nuclear powered steam turbines where maximum allowable steam flow is limited by the licensed reactor power, excessive flow margin results in efficiency losses. In addition, two-phase flow effects were often inadequately predicted in many nuclear turbine designs and have contributed to reduced first stage exit pressure, increased flow capacity, and a resultant off-design performance of the first turbine stage. These effects require excess throttling of the control valves to maintain licensed reactor power. These same two-phase effects also reduce extraction pressures of the turbine feedwater heaters resulting in reduced final feedwater temperature and enthalpy. These latter effects culminate in a red~ction in steam generator flow in order to maintain warranted power at the licensed level producing further throttling of the control valves. If the flow margin is reduced, the risk of inadequate power is increased.
Increasing the number of valve points would allow reduction of the amount of flow that might be throttled at rated power. Referring to FIG. l, an - 3 - 56,267 examination of the valve loops lO and 12 in comparison with the valve loops 14, 16, and 18 will readily demonstrate the heat rate improvemsnt in adding a valve point at 87.5 percent ~low and at 62.5 percent flow. However, each valve point requires addition of a control valve and its attendant steam piping with a significant increase in capital cost.
In general, partial arc admission provides a limited range of control and is combined with some degree of throttling of input steam. For example, the first stage flow area of a turbine may be divided into four, six, or eight partial arcs o~ admission with the smallest arc representing 12% of the first stage nozzle area. Clearly, if the flow margin is set at a maximum of 5%, some degree of throttling is requiredt with an attendant loss of efficiency, if steam flow is to be varied by an increment less than 12%. In partial arc turbines, each arc of admission, whether it be 25% or 12.5%, is associated with a separately controllable steam control valve so that steam flow to each arc can be controlled. Each control valve is relatively large and coupled to steam pipes of several inches in diameter in order to accommodate the large flow rates in power utility turbines. Most turbines of the partial arc type are so crowded by control valves and piping that additional val~es and their associated steam piping are not practical thus prohibiting use of valves capable of control partial arc segments to less than 5%. It is desirable, therefore, to provide a method and apparatus for regulating steam flow in increments less than 5%
without the steam throttling and without adding additional control valves and piping.
~8~
- 4 56, 267 SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for establishing incremental first stage flow control without throttling or addition of flow control valves.
The above and other objects and advantages are attained in one form in a steam turbine having a first stage nozzle block with a plurality, e.g., one hundred, nozzles in which a predetermined number of nozzles are selectively blocked to preclude steam flow therethrough. Preferably, a plug is radially inserted into the nozzle block into a position for blocking steam flow into one or more spaces between adjacent nozzle vanes. In a nozzle block having one hundred nozzles, use of four such plugs would permit a reduction of up to 4% of the flow area. The plugs could be actuated by hydraulic or pneumatic cylinders or by electromagnetic coils. Springs could be used to assure retraction of the plugs. Preferably, the plugs are insertable or withdrawable individually to enable incremental control of the flow area. Control is simplified by positioning the plugs in either a fully closed or fully open position.
DETAILED DESCRIPTION OF THE INVENTION
An explanation and description of a partial arc admission steam turbine is set forth in U.S. Patent No. 4,780,057, assigned to the assignee of the present invention, the disclosure of which is incorporat~d by reference. In the aforementioned patent, a simple partial arc admission syst~m has six segments of arc, six corresponding nozzle chambers, and six control valves, one for each nozzle chamber. Steam through 2 ~
It is an object of the present invention to provide a method and apparatus for establishing incremental first stage flow control without throttling or addition of flow control valves.
The above and other objects and advantages are attained in one form in a steam turbine having a first stage nozzle block with a plurality, e.g., one hundred, nozzles in which a predetermined number of nozzles are selectively blocked to preclude steam flow therethrough. Preferably, a plug is radially inserted into the nozzle block into a position for blocking steam flow into one or more spaces between adjacent nozzle vanes. In a nozzle block having one hundred nozzles, use of four such plugs would permit a reduction of up to 4% of the flow area. The plugs could be actuated by hydraulic or pneumatic cylinders or by electromagnetic coils. Springs could be used to assure retraction of the plugs. Preferably, the plugs are insertable or withdrawable individually to enable incremental control of the flow area. Control is simplified by positioning the plugs in either a fully closed or fully open position.
DETAILED DESCRIPTION OF THE INVENTION
An explanation and description of a partial arc admission steam turbine is set forth in U.S. Patent No. 4,780,057, assigned to the assignee of the present invention, the disclosure of which is incorporat~d by reference. In the aforementioned patent, a simple partial arc admission syst~m has six segments of arc, six corresponding nozzle chambers, and six control valves, one for each nozzle chamber. Steam through 2 ~
5 - 56,267 each control valve is directed into a corresponding arcuate group of stationary nozzle blades, the six nozzle blade groups forming a nozzle ring. The nozzle b]ade groups direct steam on a rotating blade row connected in driving relationship to a turbine shaft.
During turbine start-up, a control system succinctly opens the steam control valve and admits steam through the nozzle chambers in a predetermined se~uence. Steam may be throttled by gradual opening of each control valve. Valve points are established at each steam flow rate at which a valve is in a fully open position. Referring to FIG. l, valve points are established for one arrangement of control valves at 100% admission, 87.5% admission, 75% admission, 62.5%
admission, and so forth for a turbine system having eiyht control valves. For a four valve turbine, valve points may be set at 25%, 5~%, and 75% admission. In the graph of FIG. l, the loss of efficiency during throttling is evident by the higher heat rate as each valve is gradually opened (or closed). For example, at 87.5% admission corresponding to 3.4 pounds per hour (1.54 kg/hr) of steam flow, the heat rate for the four valve system is at about 7933 BT~/KWH. Each of the valve loops lO, 12, 14 for the eight valve system indicate a deviation from the ideal curve at 16.
From the above description, it will be apparent that the ideal curve at 16 could be achieved in a turbine by incorporating an infinite number of control valves and corresponding nozzle segments. However, as discussed above, the practical limit for most turbines is in the range of eight control valves simply from the limits on size and amount of steam piping connectable to the turbine. With regard to providing separate control valves for small increments of a nozzle ring, e.g., for 1% increments, the same 2~ .3 - 6 - 56,267 objection on size limitations occurs, even if the number of valves for such small increments were limited t~, for example, four valves.
Applicants have determined that for small increments of control, for example, for increments of about 1%, a turbine system can be operated or contrGlled by either fully opening or fully closing such incremental controls without inducing undesirable shock loads into downstream rotating blades.
Furthermore, if only a limited number of such incremental controls are utilized, the power input to a nuclear powered steam turbine can be regulated to its desired value without using throttling and thus avoiding the efficiency loss associated with throttling.
/Turning now to FIG. 2, there is shown a simplified, partial cross-section of a steam turbine 18 adjacent a first stage nozzle ring and downstream rotating blade row in which the teachings of the present invention are implemented~ An annular nozzle ring 20 is held in an operative position in the turbine between an outer casing 22 and an inner casing 24. The nozzle ring 20 includes an outer annular shroud 26 and an inner annular shroud 28. A plurality of uniformly, circumferentially spaced nozzles 30 extend between the shrouds 26, 28. The nozzles 30 are sometimes referred to as nozzle guide vanes or simply as stationary blades. The space 32 between inner and outer casings 24, 26 defines a nozzle chamber for receiving steam from a control valve (not shown) and directing the steam into the nozzles 30. The nozzles 30 direct the steam into the first stage rotating blades 34. The blades 34 are arranged in an annular group between an outer shroud member 36 and an inner root member 38. The root member 3B is coupled to a 2 ~ r3 $
During turbine start-up, a control system succinctly opens the steam control valve and admits steam through the nozzle chambers in a predetermined se~uence. Steam may be throttled by gradual opening of each control valve. Valve points are established at each steam flow rate at which a valve is in a fully open position. Referring to FIG. l, valve points are established for one arrangement of control valves at 100% admission, 87.5% admission, 75% admission, 62.5%
admission, and so forth for a turbine system having eiyht control valves. For a four valve turbine, valve points may be set at 25%, 5~%, and 75% admission. In the graph of FIG. l, the loss of efficiency during throttling is evident by the higher heat rate as each valve is gradually opened (or closed). For example, at 87.5% admission corresponding to 3.4 pounds per hour (1.54 kg/hr) of steam flow, the heat rate for the four valve system is at about 7933 BT~/KWH. Each of the valve loops lO, 12, 14 for the eight valve system indicate a deviation from the ideal curve at 16.
From the above description, it will be apparent that the ideal curve at 16 could be achieved in a turbine by incorporating an infinite number of control valves and corresponding nozzle segments. However, as discussed above, the practical limit for most turbines is in the range of eight control valves simply from the limits on size and amount of steam piping connectable to the turbine. With regard to providing separate control valves for small increments of a nozzle ring, e.g., for 1% increments, the same 2~ .3 - 6 - 56,267 objection on size limitations occurs, even if the number of valves for such small increments were limited t~, for example, four valves.
Applicants have determined that for small increments of control, for example, for increments of about 1%, a turbine system can be operated or contrGlled by either fully opening or fully closing such incremental controls without inducing undesirable shock loads into downstream rotating blades.
Furthermore, if only a limited number of such incremental controls are utilized, the power input to a nuclear powered steam turbine can be regulated to its desired value without using throttling and thus avoiding the efficiency loss associated with throttling.
/Turning now to FIG. 2, there is shown a simplified, partial cross-section of a steam turbine 18 adjacent a first stage nozzle ring and downstream rotating blade row in which the teachings of the present invention are implemented~ An annular nozzle ring 20 is held in an operative position in the turbine between an outer casing 22 and an inner casing 24. The nozzle ring 20 includes an outer annular shroud 26 and an inner annular shroud 28. A plurality of uniformly, circumferentially spaced nozzles 30 extend between the shrouds 26, 28. The nozzles 30 are sometimes referred to as nozzle guide vanes or simply as stationary blades. The space 32 between inner and outer casings 24, 26 defines a nozzle chamber for receiving steam from a control valve (not shown) and directing the steam into the nozzles 30. The nozzles 30 direct the steam into the first stage rotating blades 34. The blades 34 are arranged in an annular group between an outer shroud member 36 and an inner root member 38. The root member 3B is coupled to a 2 ~ r3 $
- 7 ~ 56~267 portion 40 of a turbine shaft (not shown) such that steam impinging on blades 34 effects rotation of the shaft. A seal 42 prevents steam leakage around blades 34 while a seal 44 prevents leakage between the nozzle ring 20 and inner cylinder 46.
The present invention utilizes a plurality, for example, four, plug members 48 positionad in outer casing 2~ at locations adjacent selected ones of the spaces between adjacent nozzles 30. In a preferred form, the plug members 48 have a circumferential width corresponding to nozzle pitch whereby steam flow between an adjacent pair of nozzles 30 can be blocked by one plug member. However, it is recognized that the width of a plug member could be selected to block more than one such space. The plug member 48 can be forced into the closed position illustrated in FIG. 2 using a high pressure fluid, i.e., hydraulic or pneumatic, introduced through line 50 into a cavity 52. The plug member 48 may be formed with a head portion 54 acting as a piston with sealing rings 56 between the head portion and the inner walls of the cavity 52. A spring 58 under the head portion 54 retracts the plug member 48 when fluid pressure i5 released from above the head portion. The body 60 of 2S member 48 slides within a guide cylinder 62 formed in outer casing 22.
~ Turning now to FIG. 3, there is shown a radial view of a portion of an arc of admission in which two plug members 48 are shown in position for blocking flow through selected nozzle passages. In order to minimize the shock effect as the rotating blades 34 pass by the nozzle passage which has been blocked (thus passing in and out of a reduced flow area), the plug member 48 may be spaced several nozzles apart.
The present invention utilizes a plurality, for example, four, plug members 48 positionad in outer casing 2~ at locations adjacent selected ones of the spaces between adjacent nozzles 30. In a preferred form, the plug members 48 have a circumferential width corresponding to nozzle pitch whereby steam flow between an adjacent pair of nozzles 30 can be blocked by one plug member. However, it is recognized that the width of a plug member could be selected to block more than one such space. The plug member 48 can be forced into the closed position illustrated in FIG. 2 using a high pressure fluid, i.e., hydraulic or pneumatic, introduced through line 50 into a cavity 52. The plug member 48 may be formed with a head portion 54 acting as a piston with sealing rings 56 between the head portion and the inner walls of the cavity 52. A spring 58 under the head portion 54 retracts the plug member 48 when fluid pressure i5 released from above the head portion. The body 60 of 2S member 48 slides within a guide cylinder 62 formed in outer casing 22.
~ Turning now to FIG. 3, there is shown a radial view of a portion of an arc of admission in which two plug members 48 are shown in position for blocking flow through selected nozzle passages. In order to minimize the shock effect as the rotating blades 34 pass by the nozzle passage which has been blocked (thus passing in and out of a reduced flow area), the plug member 48 may be spaced several nozzles apart.
- 8 - 56,267 While the principles of the invention have now been made clear in an illustrative embodiment, it will become apparent to those skilled in the art that many modifications of the structures, arrangements, and components presented in the above illustrations may be made in the practice of the invention in order to develop alternate embodiments suitable to specific operating requirements without departing from the spirit and scope of the invention as set forth in the claims which follow.
Claims (7)
1. A method of minimizing heat rate impairment from excess flow margin in a power system including a steam turbine having a first stage nozzle ring comprising a plurality of circumferentially spaced nozzle blades with steam passages defined between each adjacent pair of blades, power output being determined at least in part by the volume of steam flow through the nozzle ring, the turbine including a plurality of plug members each selectively insertable into a position for blocking steam flow passages, and at least one control valve for throttling steam flow into the turbine, the method comprising the steps of:
determining when the steam flow through the control valve exceeds a desired flow rate value for the power system; and inserting selected ones of the plug members into their operative position adjacent the nozzle ring to reduce the flow rate to the desired value.
- 10 - 56,267
determining when the steam flow through the control valve exceeds a desired flow rate value for the power system; and inserting selected ones of the plug members into their operative position adjacent the nozzle ring to reduce the flow rate to the desired value.
- 10 - 56,267
2. The method of claim 1 wherein each of the plug members is positioned to block steam flow to only one steam flow passage.
3. The method of claim 1 wherein each plug member is fluid pressure actuated and mechanically retracted, the method further comprising the steps of retracting the plug members when steam flow is less than the desired flow rate.
4. Apparatus for minimizing heat rate impairment due to excess flow margin in a steam turbine system including a steam turbine having a first stage nozzle ring comprising a plurality of circumferentially spaced nozzle blades for directing steam flow in a predetermined direction into a first rotating blade row, the apparatus comprising at least one plug member selectively insertable into the turbine adjacent an inlet side of the nozzle ring for blocking steam flow through at least one passage between adjacent nozzle blades for reducing steam flow rates without valve throttling.
5. The apparatus of claim 4 wherein the turbine system comprises a nuclear powered steam generator having steam capacity greater than licensed reactor power for the system, the turbine being provided with a plurality of plug members for blocking steam flow through the nozzle ring at preselected spaced locations for reducing steam flow rate to a value corresponding to the licensed reactor power.
- 11 - 56,267
- 11 - 56,267
6. The apparatus of claim 4 wherein the at least one plug member is positioned within a guide cylinder formed in an outer casing portion of the steam turbine, the cylinder being coupled to a fluid actuator for pressurizing the cylinder to force the at least one plug member into an operative position for blocking steam flow through at least one passage in the nozzle ring.
7. The apparatus of claim 6 and including spring means coupled to said plug member for forcing said plug member into a retracted position upon release of said pressurizing fluid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US63772091A | 1991-01-07 | 1991-01-07 | |
| US637,720 | 1991-01-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2058815A1 true CA2058815A1 (en) | 1992-07-08 |
Family
ID=24557106
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2058815 Abandoned CA2058815A1 (en) | 1991-01-07 | 1992-01-06 | Method of improving the rated load heat rate of steam turbines |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPH04295104A (en) |
| CA (1) | CA2058815A1 (en) |
| ES (1) | ES2052424B1 (en) |
| IT (1) | IT1252713B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101625794B1 (en) * | 2015-04-06 | 2016-05-30 | 두산중공업 주식회사 | Nozzle box for turbine |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6131604A (en) * | 1984-07-25 | 1986-02-14 | Ishikawajima Harima Heavy Ind Co Ltd | Plugging method for low-temperature turbine nozzle |
| US4780057A (en) * | 1987-05-15 | 1988-10-25 | Westinghouse Electric Corp. | Partial arc steam turbine |
| US4840537A (en) * | 1988-10-14 | 1989-06-20 | Westinghouse Electric Corp. | Axial flow steam turbine |
-
1991
- 1991-12-24 IT ITMI913490A patent/IT1252713B/en active IP Right Grant
-
1992
- 1992-01-03 ES ES9200005A patent/ES2052424B1/en not_active Expired - Lifetime
- 1992-01-06 CA CA 2058815 patent/CA2058815A1/en not_active Abandoned
- 1992-01-07 JP JP89692A patent/JPH04295104A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| ITMI913490A1 (en) | 1993-06-24 |
| ES2052424A2 (en) | 1994-07-01 |
| ES2052424B1 (en) | 1997-01-01 |
| JPH04295104A (en) | 1992-10-20 |
| ES2052424R (en) | 1996-05-16 |
| ITMI913490A0 (en) | 1991-12-24 |
| IT1252713B (en) | 1995-06-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |